Epithelial cells often require polarization in two axes for their function, (1) ubiquitous apical-basal polarity and (2) a second axis within the plane of the epithelium, the latter called Planar Cell Polarity (PCP). Typical mammalian PCP examples are highlighted by the organization of the skin and many internal organs, e.g. the inner ear with its sensory cilia, and, importantly, also include directed cell migration during mammalian gastrulation and neural tube closure. In Drosophila, all adult cuticular structures show PCP features. The establishment of PCP in Drosophila serves as a paradigm to study PCP determination in mammalian development and human disease. PCP is coordinated by the activity of the Frizzled (Fz) receptor (with Wnt family members as their ligands) and its associated signaling cascade (Fz/PCP signaling), highly conserved throughout evolution. It not only regulates many aspects of cellular polarization, but also impacts coordinated and directed cell migration. Whereas the framework of PCP signaling is beginning to be established, its specific links to the regulatory feed into cell motility, cell migration, and associated biophysical changes in the responding cells remain largely unknown. The scope of this application is to establish the technology and analytical tools to allow an automated dissection and quantification of PCP regulated cell motility features at cell-biological levels. We will use the Drosophila eye as model system, as it provides unique advantages through its sophisticated genetic tools and available molecular markers. The goal is to establish imaging protocols and quantitative tools to allow the formulation of a biophysical model of PCP-regulated cell motility in the eye that then will serve as the paradigm for molecular disease oriented dissections of related processes. We will use a combination of Drosophila in vivo studies, a novel in vivo time-lapse imaging protocol for fly eye development, and mathematical quantitative analyses to define the critical parameters governed by PCP signaling that impact cell motility through, for example, junctional remodeling and associated cellular mechanic forces. Several components of PCP signaling and its associated downstream regulatory effectors are critically linked to neural tube closure defects (a prevalent child health development issue and frequent cause of late miscarriages or early embryonic death); in addition several other diseases, including cancer, and also stem cell biology features are linked to the molecules studied here. Thus, the information acquired in this application will not only advance our understanding of regulated cellular motility, but it will also be of medical relevance in many disease associated contexts.